1. Field of the Invention
The present invention relates to an electric motor with a brush plate and in particular, to a universal motor for use in an electrical hand-held power tool.
2. Description of the Prior Art
With electric motors described above, usually, the brush plate is separately screwed in the housing.
German Publication DE 36 36 539 discloses a universal motor for an electrical hand-held power tool which is mounted in a two-part housing that is screwed with two screws. Both parts of the housing are formed as pot-shaped parts. On one of the housing parts, there are provided projections which a brush plate made of a plastic material abuts in the axial direction. In an opposite axial direction, the brush plate lies on the plastic base of the stator and is secured, together with the stator, axially in the housing with screws.
German Publication DE 101 53 574 discloses a rotatable brush plate with a plurality of circumferentially distributed hooks formed thereon. The hooks lockingly axially engage from behind associated ribs provided in the housing. Thereby, the brush plate is permanently axially secured in the housing. Tensioning and bending forces, which are necessarily generated by concave hooks, produce local stresses in a brush plate formed of a plastic material. These stresses are generated outside of the reversibly elastically deformable region. Therefore, because of the viscoelastic behavior of the material, retardation of the material and of the hooks takes place. As a result, with time, loss of the axial locking takes place. High temperatures, which are usually observed with universal motors of hand-held power tools, accelerate this behavior.
Accordingly, an object of the present invention is to provide long-lasting means, in particular, suitable for mass production, for reliably axially securing a brush plate.